Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$174.50	13.731%	$198.4606	$198.46	$198.45	$198.50
Purchase #2	$77.39	3.397%	$80.0189	$80.02	$80.00	$80.00
Purchase #3	$85.27	6.396%	$90.7239	$90.72	$90.70	$90.70
Purchase #4	$75.84	11.781%	$84.7747	$84.77	$84.75	$84.80
Purchase #5	$93.69	6.829%	$100.0881	$100.09	$100.10	$100.10
Purchase #6	$79.47	11.287%	$88.4398	$88.44	$88.45	$88.40
Purchase #7	$247.67	9.579%	$271.3943	$271.39	$271.40	$271.40
7 purchase totals =	$833.83		$913.9003	$913.89	$913.85	$913.90